<div class="refentry" lang="en" xml:lang="en"><a id="glXGetConfig"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glXGetConfig — return information about GLX visuals</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table><tr><td><code class="funcdef">int <b class="fsfunc">glXGetConfig</b>(</code></td><td>Display *  </td><td><var class="pdparam">dpy</var>, </td></tr><tr><td> </td><td>XVisualInfo *  </td><td><var class="pdparam">vis</var>, </td></tr><tr><td> </td><td>int  </td><td><var class="pdparam">attrib</var>, </td></tr><tr><td> </td><td>int *  </td><td><var class="pdparam">value</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>dpy</code></em></span></dt><dd><p>
                    Specifies the connection to the X server.
                </p></dd><dt><span class="term"><em class="parameter"><code>vis</code></em></span></dt><dd><p>
                    Specifies the visual to be queried.
                    It is a pointer to an <code class="constant">XVisualInfo</code> structure,
                    not a visual ID or a pointer to a <code class="constant">Visual</code>.
                </p></dd><dt><span class="term"><em class="parameter"><code>attrib</code></em></span></dt><dd><p>
                    Specifies the visual attribute to be returned.
                </p></dd><dt><span class="term"><em class="parameter"><code>value</code></em></span></dt><dd><p>
                    Returns the requested value.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glXGetConfig</code> sets <em class="parameter"><code>value</code></em> to the <em class="parameter"><code>attrib</code></em> value of windows or GLX pixmaps
            created with respect to <em class="parameter"><code>vis</code></em>.
            <code class="function">glXGetConfig</code> returns an error code if it fails for any reason.
            Otherwise, zero is returned.
        </p><p>
            <em class="parameter"><code>attrib</code></em> is one of the following:
        </p><p>
        </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GLX_USE_GL</code></span></dt><dd><p>
                        <code class="constant">True</code> if OpenGL rendering is supported by this visual,
                        <code class="constant">False</code> otherwise.
                    </p></dd><dt><span class="term"><code class="constant">GLX_BUFFER_SIZE</code></span></dt><dd><p>
                        Number of bits per color buffer.
                        For RGBA visuals, <code class="constant">GLX_BUFFER_SIZE</code> is the sum of
                        <code class="constant">GLX_RED_SIZE</code>,
                        <code class="constant">GLX_GREEN_SIZE</code>,
                        <code class="constant">GLX_BLUE_SIZE</code>, and
                        <code class="constant">GLX_ALPHA_SIZE</code>.
                        For color index visuals, <code class="constant">GLX_BUFFER_SIZE</code> is the size of the
                        color indexes.
                    </p></dd><dt><span class="term"><code class="constant">GLX_LEVEL</code></span></dt><dd><p>
                        Frame buffer level of the visual.
                        Level zero is the default frame buffer.
                        Positive levels correspond to frame buffers that overlay the default buffer,
                        and negative levels correspond to frame buffers that underlay the default
                        buffer.
                    </p></dd><dt><span class="term"><code class="constant">GLX_RGBA</code></span></dt><dd><p>
                        <code class="constant">True</code> if color buffers store red, green, blue, and alpha values.
                        <code class="constant">False</code> if they store color indexes.
                    </p></dd><dt><span class="term"><code class="constant">GLX_DOUBLEBUFFER</code></span></dt><dd><p>
                        <code class="constant">True</code> if color buffers exist in front/back pairs that can be swapped,
                        <code class="constant">False</code> otherwise.
                    </p></dd><dt><span class="term"><code class="constant">GLX_STEREO</code></span></dt><dd><p>
                        <code class="constant">True</code> if color buffers exist in left/right pairs,
                        <code class="constant">False</code> otherwise.
                    </p></dd><dt><span class="term"><code class="constant">GLX_AUX_BUFFERS</code></span></dt><dd><p>
                        Number of auxiliary color buffers that are available.
                        Zero indicates that no auxiliary color buffers exist.
                    </p></dd><dt><span class="term"><code class="constant">GLX_RED_SIZE</code></span></dt><dd><p>
                        Number of bits of red stored in each color buffer.
                        Undefined if <code class="constant">GLX_RGBA</code> is <code class="constant">False</code>.
                    </p></dd><dt><span class="term"><code class="constant">GLX_GREEN_SIZE</code></span></dt><dd><p>
                        Number of bits of green stored in each color buffer.
                        Undefined if <code class="constant">GLX_RGBA</code> is <code class="constant">False</code>.
                    </p></dd><dt><span class="term"><code class="constant">GLX_BLUE_SIZE</code></span></dt><dd><p>
                        Number of bits of blue stored in each color buffer.
                        Undefined if <code class="constant">GLX_RGBA</code> is <code class="constant">False</code>.
                    </p></dd><dt><span class="term"><code class="constant">GLX_ALPHA_SIZE</code></span></dt><dd><p>
                        Number of bits of alpha stored in each color buffer.
                        Undefined if <code class="constant">GLX_RGBA</code> is <code class="constant">False</code>.
                    </p></dd><dt><span class="term"><code class="constant">GLX_DEPTH_SIZE</code></span></dt><dd><p>
                        Number of bits in the depth buffer.
                    </p></dd><dt><span class="term"><code class="constant">GLX_STENCIL_SIZE</code></span></dt><dd><p>
                        Number of bits in the stencil buffer.
                    </p></dd><dt><span class="term"><code class="constant">GLX_ACCUM_RED_SIZE</code></span></dt><dd><p>
                        Number of bits of red stored in the accumulation buffer.
                    </p></dd><dt><span class="term"><code class="constant">GLX_ACCUM_GREEN_SIZE</code></span></dt><dd><p>
                        Number of bits of green stored in the accumulation buffer.
                    </p></dd><dt><span class="term"><code class="constant">GLX_ACCUM_BLUE_SIZE</code></span></dt><dd><p>
                        Number of bits of blue stored in the accumulation buffer.
                    </p></dd><dt><span class="term"><code class="constant">GLX_ACCUM_ALPHA_SIZE</code></span></dt><dd><p>
                        Number of bits of alpha stored in the accumulation buffer.
                    </p></dd></dl></div><p>
            The X protocol allows a single visual ID to be instantiated with
            different numbers of bits per pixel.
            Windows or GLX pixmaps that will be rendered with OpenGL, however,
            must be instantiated with a color buffer depth of <code class="constant">GLX_BUFFER_SIZE</code>.
        </p><p>
            Although a GLX implementation can export many visuals that support GL
            rendering,
            it must support
            at least one RGBA visual. This visual must have at
            least one color buffer,
            a stencil buffer of at least 1 bit,
            a depth buffer of at least 12 bits,
            and an accumulation buffer.
            Alpha bitplanes are optional in this visual.
            However,
            its color buffer size must be as great as that of the
            deepest <code class="constant">TrueColor</code>, <code class="constant">DirectColor</code>,
            <code class="constant">PseudoColor</code>, or <code class="constant">StaticColor</code> visual supported on level zero,
            and it must itself be made available on level zero.
        </p><p>
            In addition, if the X server exports a <code class="constant">PseudoColor</code>
            or <code class="constant">StaticColor</code> visual on framebuffer level 0, a color index
            visual is also required on that level.
            It must have
            at least one color buffer,
            a stencil buffer of at least 1 bit,
            and a depth buffer of at least 12 bits.
            This visual must
            have as many
            color bitplanes as the deepest
            <code class="constant">PseudoColor</code> or <code class="constant">StaticColor</code> visual supported on level 0.
        </p><p>
            Applications are best written to select the visual that most closely
            meets their requirements.
            Creating windows or GLX pixmaps with unnecessary buffers can result in
            reduced rendering performance as well as poor resource allocation.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
            <code class="constant">XVisualInfo</code> is defined in <span class="emphasis"><em>Xutil.h.</em></span>
            It is a structure that includes <span class="emphasis"><em>visual</em></span>, <span class="emphasis"><em>visualID</em></span>, <span class="emphasis"><em>screen</em></span>, and
            <span class="emphasis"><em>depth</em></span> elements.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GLX_NO_EXTENSION</code> is returned if <em class="parameter"><code>dpy</code></em> does not support the GLX
            extension.
        </p><p>
            <code class="constant">GLX_BAD_SCREEN</code> is returned if the screen of <em class="parameter"><code>vis</code></em> does not correspond
            to a screen.
        </p><p>
            <code class="constant">GLX_BAD_ATTRIBUTE</code> is returned if <em class="parameter"><code>attrib</code></em> is not a valid GLX attribute.
        </p><p>
            <code class="constant">GLX_BAD_VISUAL</code> is returned if <em class="parameter"><code>vis</code></em> doesn't support GLX and an
            attribute other than <code class="constant">GLX_USE_GL</code> is requested.
        </p></div>
        {$pipelinestall}{$examples}
        <div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glXChooseVisual"><span class="citerefentry"><span class="refentrytitle">glXChooseVisual</span></span></a>,
            <a class="citerefentry" href="glXCreateContext"><span class="citerefentry"><span class="refentrytitle">glXCreateContext</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><div id="Copyright"><h2>Copyright</h2><p>
            Copyright © 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></div>
